High in the canopy, this treetop symphony at once strengthens the bond between the pair of siamangs and declares their territory to others in the area. The song can be heard from over a mile away even in our urban environment and, as they develop their tune, the bouts may last up to 20 minutes.

How do they project their voices so far? Those ballooning throat sacs act like a resonating chamber and amplify the sound.

Briony’s tune with her former long-time mate Simon was known by not just zoo visitors, but also neighbors in Phinney Ridge, Fremont and Wallingford, all within earshot of their morning song.

Hearing the treetops come to life in siamang song once again is an encouraging sign of Sam’s and Briony’s growing bond, and a piercing reminder of what’s at stake in a world where siamangs face the threat of extinction in the wild.

The largest of the gibbon species, siamangs are native to forests of Asia that are disappearing at alarming rates as human development and agriculture expand. In this Year of the Gibbon, as declared by the International Union for Conservation of Nature, our work continues in the field where conservation scientists supported by the Association of Zoos and Aquariums Ape Taxon Advisory Group—a Woodland Park Zoo Wildlife Survival Fund project—are empowering local communities to become stewards of gibbon conservation.